(214a) Microneedle-Based Immunization against Influenza

Influenza virus is one of the common causes of serious respiratory illness. Typically, the virus causes seasonal epidemics of disease; during a typical season 36,000 deaths and 200,000 hospitalizations are observed, with up to 1.5 million deaths worldwide, which make it the largest cause of death in the US from vaccine-preventable disease. The vaccines do not prevent infection, but result in a reduction of disease severity and transmission.

The composition of the influenza vaccine is determined annually based on the strains of virus that are expected to be circulating in the human population just a few months before the vaccination season. As a result, the production, storage and distribution of the necessary amount of vaccine puts a lot of pressure on the pharmaceutical industry. Improved vaccine coverage is needed, which can be facilitated by better delivery methods.

In this study we investigated a novel way to facilitate and enhance influenza vaccination, based on arrays of microscopic needles (microneedles) coated with inactivated influenza vaccine. Using dozens of microneedles coated with influenza vaccine, the vaccine will be delivered in a painless yet simple patch-like manner. An additional advantage of intradermal delivery of vaccine is that the upper layers of skin are rich with antigen presenting immune cells which makes vaccine delivery to these areas more efficient. Intradermally delivered vaccine indeed showed better efficacy in elder population. Because vaccine is stored and administered in the solid state, vaccine stability may be sufficient for storage and distribution at room temperature. In addition, this approach may also address other limitations of the current injectable vaccine, including its limited breadth and duration of immunity, and its lack of effective mucosal immune responses.

In this study, microneedles were coated by a dip coating method. In order to achieve an adequate coating and good wetting of microneedle tips, thickening and surfactant additives were used during the process. At the final stage the coating solution was dried on microneedle tips at room temperature and humidity. Drying of vaccine during coating may potentially damage the immunogenicity of vaccine. By varying thickening agents, buffer composition and protective additives we optimized the coating composition and condition in order to achieve optimal amount of coated vaccine and its mechanical and biological stability. Under current conditions it is possible to coat up to 2 micrograms of vaccine per individual needle.

In order to address the vaccine activity we measured the hemagglutination activity (HA) of vaccine after drying on microneedles. This test gives a quick measurement of the activity of surface receptors of influenza with the only downside of possible false-negative outcome to predict antigenicity in vivo. Optimized formulations were found to retain more than 25% of its original activity.

The immunogenic activity of vaccine was tested by vaccination of groups of Balb/c female mice with 10 micrograms of influenza vaccine. The groups of mice were vaccinated by conventional IM injections or by coated microneedles containing H1N1 or H3N2 vaccines. The efficiency of immunization was measured by antibody-specific IgG titer and hemagglutination inhibition (HAI) in plasma. These measurements confirmed that microneedle delivered vaccine is able to increase the level of protective antibodies in blood compared to naïve mice.

At the final step the protection caused by induction of cellular and humoral immune systems was measured by challenging groups of mice by lethal doze of live influenza virus (5 x LD50). Both microneedle vaccine and the positive control IM groups showed good protection against this challenge.

In conclusion, our results showed that vaccine coated on microneedles is easy to administer and provides sufficient protection to mice even after a single vaccination (priming) and even better protection after double vaccination (priming and boosting).